Research shows blocking persistence increases when solar activity is low, causing weather patterns to become locked in place at high and intermediate latitudes for prolonged periods of time.
During a solar minimum, the jet stream’s usual Zonal Flow (a west–east direction) reverts to more of a Meridional Flow (a north-south direction).
This is exaggerated further during a Grand Solar Minimum, like the one we’re entering now, and explains why regions become unseasonably hot or cold and others unusually dry or rainy, with the extremes lasting for an extended period of time.
Mikhaël Schwander, et al, 2017 — “The zonal flow characteristic of westerly types is reduced under low solar activity as the continental flow for easterly and northerly types is enhanced. This is also confirmed by the higher blocking frequency over Scandinavia under low solar activity.”
And the paper goes further:
“The 247-year-long analysis of the 11-year solar cycle impact on late winter European weather patterns suggests a reduction in the occurrence of westerly flow types linked to a reduced mean zonal flow under low solar activity. Based on this observational evidence, we estimate the probability to have cold conditions in winter over Europe to be higher under low solar activity than under high activity.”— Mikhaël Schwander, et al, 2017
Last winter a blocking high over Scandinavia lead to bitterly cold air funnelling in over the UK from eastern Europe/Russia — the ‘Beast from the East’.
It lasted for months and led to record snow in Ireland and Britain.
With the sun slipping into what’s know as a Grand Solar Minimum — a prolonged period of solar decline — these blocking highs are only going to become more prevalent.
Even mainstream weather forecasters feel the need to explain the phenomenon.
Here’s the long-range forecast from the Met Office:
“By mid-November, there are signals for high pressure to develop to the north of the UK, with ‘blocked’ conditions becoming established.
“Temperatures are likely to be mostly below normal, with a greater likelihood of frost as well as some snow for higher ground in the north. Any milder spells are likely to be short-lived.”
We can expect the European winter of 2018/19 to be truly brutal, with record cold temperatures and snow accumulations.